In patients with acute myocardial infarction (AMI), the extent of wall motion abnormality is an important determinant of global left ventricular (LV) function and prognosis. However, the regional distortion of LV anatomy in AMI prevents an accurate assessment of the magnitude of LV dysfunction with currently available methods. Real-time 3-dimensional echocardiography (RT-3D echo) is a novel technique that provides instantaneous volumetric images which permit unrestricted visualization of LV wall motion. The purpose of this study was to develop and validate a methodology for quantitative assessment of wall motion abnormalities in patients with AMI. To this end, 36 patients (28 men; age 65+/-14 years), diagnosed with first AMI based on clinical criteria and serial enzyme elevation, underwent RT-3D echo within 24 hours of admission. Images were acquired from an apical window and stored for blinded off-line analysis. Quantitative assessment of regional LV dysfunction was achieved by tracing the area of wall motion abnormality on a Silicone Graphics workstation and expressed in absolute terms (cm2) and as a percent of total LV endocardium. Peak troponin I levels ranged from 2.3 to 416 ng/ml (mean 69+/-88) and peak myoglobin levels ranged from 24 to 2730 ng/ml (mean 507+/-720). The area of wall motion abnormality ranged from 0 to 71 cm2 (mean 17+/-14) or 0% to 44% of total LV endocardium (mean 13%+/-10%). A strong correlation was observed between peak troponin I levels and area of wall motion abnormality expressed in absolute terms (r=0.81; p<0.0001) or as a percent of total LV endocardium (r=0.79; p<0.0001). A significant but weaker correlation was observed between peak myoglobin levels and area of wall motion abnormality expressed in absolute terms (r=0.51; p=0.003) or as a percent of total LV endocardium (r=0.54; p<0.002). Thus, in patients with AMI, RT-3D echo allows a quantitative assessment of wall motion abnormalities which correlates with independent measures of infarct size. This methodology may therefore be useful to determine the extent of LV dysfunction and thus aid in the risk stratification of these patients.